---
title: "Add reaction"
method: POST
path: "/v1/inbox/conversations/{conversationId}/messages/{messageId}/reactions"
tags: ["Messages"]
---

# Add reaction

`POST /v1/inbox/conversations/{conversationId}/messages/{messageId}/reactions`

Add an emoji reaction to a message. Platform support:
- Telegram: Supports a subset of Unicode emoji reactions
- WhatsApp: Supports any standard emoji (one reaction per message per sender)
- Instagram and Facebook Messenger: Any standard emoji, subject to Meta's 24h messaging window
- Slack: The emoji must have a Slack name (e.g. `:thumbsup:`); unnamed characters return 400
- 'iMessage: The six Apple tapbacks (❤️ 👍 👎 😂 ‼️ ❓) render natively; any other emoji is sent as a custom emoji tapback (iOS 18+ recipients)'
- All others: Returns 400 (not supported)

## Path parameters

- `conversationId` string, required
- `messageId` string, required

## Request body

- object
  - `accountId` string, required — Account ID
  - `emoji` string, required — Emoji character (e.g. "👍", "❤️")

## Response `200`

The platform accepted the reaction request. This does not guarantee the reaction was placed: the platform never confirms what it acted on.

- object
  - `success` boolean
  - `messageId` string — The Zernio message ID the reaction was resolved against
  - `platformMessageId` string — The platform message ID the reaction was sent for

## Other responses

- `400` — Platform does not support reactions or invalid request
- `401` — Unauthorized
- `403` — Inbox addon required
- `404` — Account, conversation or message not found (message_not_found when messageId does not resolve to a message in this conversation)

## Changes

- **2026-08-26** `b5344d376e5e` — 2 info
  - added the optional property `messageId` to the response with the `200` status
  - added the optional property `platformMessageId` to the response with the `200` status

[Change history](https://skmtc.dev/zernio/apis/zernio-api/changes/v1/inbox/conversations/:conversationId/messages/:messageId/reactions/post.md)

---

[API](https://skmtc.dev/zernio/apis/zernio-api.md) · [All operations](https://skmtc.dev/zernio/apis/zernio-api/llms.txt) · [OpenAPI document](https://skmtc.dev/zernio/apis/zernio-api/revisions/dd3865482f9f?raw)